No abstract

Eggs from a commerical flock of Small White turkeys established at 76 meters above sea level were used to develop five lines of turkeys. Hatchability of fertile eggs was the only criterion used to establish selected lines at 76, 1524, and 2182 meters. Control lines were maintained at the 76 and 1524-meter locations. The objective of this study was to evaluate effects of the selection program on organ weights, body weight, and packed cell volumes (PCV). For two generations, eggs from one hatch at each of the three elevations were divided into three groups, two of which were exchanged for hatching and rearing. Twenty poults from the five lines at all three locations were sacrificed at 1-day, 2-weeks, and 4-weeks of age. Heart. liver spleen, adrenals, pancreas, lungs, kidneys, and gonads were removed, weighed, and the weight expressed as a percent of body weight. Blood samples were collected and PCV values determined at ages 1-day, 2-weeks, and 4-weeks at the 1524-meter elevation. Selection for hatchability had no adverse effect upon 1-day, 2, and 4-week body weights. Variations in body weight between locations were not due to natural environmental conditions, but rather to variations in management. Selection for hatchability coupled with natural selection resulted in the development of lines of turkeys with higher PCV values than the original control population. Exposure of turkey poults from the five genetic lines developed at an altitude of 2182 meters lead to an increase in relative weights of the heart and adrenal glands compared to birds at the 76 and 1524-meter locations. Exposure at the 2182-meter location also resulted in lighter spleens, pancreata, kidneys, and ovaries compared to birds at the 76 and 1524-meter locations. Selection for hatchability favors larger adrenals, livers, pancreata, kidneys, and lungs, but smaller hearts. Natural selection at higher elevations compounds the situation by favoring smaller adrenals and livers, but larger spleens, pancreata, and kidneys.

A line of medium white turkeys developed at an altitude of 105 meters above sea level was reproduced and reared at 1524 meters above sea level for seven generations. One half of the population was selected for seven generations for increased hatchability based on individual hen performance. The other half of the population was selected at random each year. Records were kept of percent hatchability, percent fertility, average number of eggs set, average egg weight, body weight at two, eight, and 20 weeks of age for all birds in each generation. When the birds were thirty-two weeks of age, body depth, keel length, and shank length were recorded for each bird in generation 6 and 7. Percent hatchability increased in both the selected and the nonselected groups during the first four generations but decreased during the last three generations. Percent hatchability and fertility in the selected group was consistently higher than in the nonselected group each generation. Average egg weight decreased in both lines. No consistently significant correlations were found between hatchability and any of the traits measured.